JP2010164541A - Processing apparatus - Google Patents

Processing apparatus Download PDF

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JP2010164541A
JP2010164541A JP2009009365A JP2009009365A JP2010164541A JP 2010164541 A JP2010164541 A JP 2010164541A JP 2009009365 A JP2009009365 A JP 2009009365A JP 2009009365 A JP2009009365 A JP 2009009365A JP 2010164541 A JP2010164541 A JP 2010164541A
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Japan
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signal
error
phase signal
amplitude
cosine
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JP2009009365A
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Japanese (ja)
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Yuzo Seo
雄三 瀬尾
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Canon Inc
キヤノン株式会社
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Priority to JP2009009365A priority Critical patent/JP2010164541A/en
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01BMEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00Instruments as specified in the subgroups and characterised by the use of optical measuring means
    • G01B9/02Interferometers for determining dimensional properties of, or relations between, measurement objects
    • G01B9/02083Interferometers for determining dimensional properties of, or relations between, measurement objects characterised by particular signal processing and presentation
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01BMEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00Instruments as specified in the subgroups and characterised by the use of optical measuring means
    • G01B9/02Interferometers for determining dimensional properties of, or relations between, measurement objects
    • G01B9/02055Interferometers for determining dimensional properties of, or relations between, measurement objects characterised by error reduction techniques
    • G01B9/02075Interferometers for determining dimensional properties of, or relations between, measurement objects characterised by error reduction techniques of particular errors
    • G01B9/02078Caused by ambiguity
    • G01B9/02079Quadrature detection, i.e. detecting relatively phase-shifted signals
    • G01B9/02081Quadrature detection, i.e. detecting relatively phase-shifted signals simultaneous quadrature detection, e.g. by spatial phase shifting
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01DMEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/244Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
    • G01D5/24471Error correction
    • G01D5/24476Signal processing
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01DMEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/244Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
    • G01D5/24471Error correction
    • G01D5/2448Correction of gain, threshold, offset or phase control
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01DMEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infra-red, visible, or ultra-violet light
    • G01D5/266Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infra-red, visible, or ultra-violet light by interferometric means
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01BMEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B2290/00Aspects of interferometers not specifically covered by any group under G01B9/02
    • G01B2290/45Multiple detectors for detecting interferometer signals

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of calculating the position or the angle which enables the correction of the effect of noise with amplitude modulation properties, at a high speed. <P>SOLUTION: The signal processing device SP calculates a cosine signal (A-A')/(A+A') and a sine signal (B-B')/(B+B') from a first normal phase signal A, a first reverse phase signal A', a second normal phase signal B having a phase different from that of the first normal phase signal A, and a second reverse phase signal B' provided from a detection device at a first calculation section 10, and applies error correction signal processing on the cosine signal and the sine signal at a second calculation section 20, calculates the position or angle of a detection object, and corrects the error. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a signal processing device that calculates the position or angle of an object to be detected based on a periodic signal provided from a detection device.

  Detection devices such as encoders and laser interferometers are used for the purpose of measuring the position or angle of the detection object. The detection device outputs sinusoidal periodic signals having a phase difference of 90 ° with the phase changing according to the position or angle of the detection target. By performing arctangent calculation on the periodic signals output from the detection device and having a phase difference of 90 °, the angle of the position of the detection object can be accurately detected.

  The periodic signal output from the detection device usually includes error components such as an offset error, an amplitude error, and a phase difference error, unlike an ideal sine wave. Patent Document 1 discloses a technique for correcting such an error component.

Noise can be superimposed on the periodic signal in a transmission line that connects the detection device and a signal processing device that processes the periodic signal output therefrom. In order to remove such noise, a technique is used in which a positive phase signal and a negative phase signal are transmitted as periodic signals, and the negative phase signal is subtracted from the positive phase signal on the receiving side. According to this technique, it is possible to cancel noise superimposed in the same manner on a transmission line that transmits a normal phase signal and a transmission line that transmits a reverse phase signal. The forward / reverse phase signal can be generated by inverting and amplifying the same signal, but two detectors can be provided to output the forward / reverse phase signal.
U.S. Pat. No. 4,458,322 US Pat. No. 5,581,488 Japanese Patent No. 2790862

  By the way, periodic signals output from detection devices such as encoders and laser interferometers include amplitude-modulating noise. Amplitude-modulating noise can be generated, for example, by fluctuations in light source intensity, noise applied to a power supply voltage of a light receiving circuit and an electronic circuit for amplifying a signal output from the light receiving circuit.

  The amplitude-modulating noise does not affect the result because the ratio of two periodic signal values is calculated in the arctangent calculation. However, the peak value of the periodic signal for correcting the offset error and the amplitude error is sensitive to amplitude-modulating noise. As a technique for correcting an offset error or an amplitude error, a technique for suppressing random noise by means such as collecting a large number of peak values and performing exponential smoothing is known (Patent Documents 2 and 3). However, in order to collect a large number of peak values, the moving distance becomes large, and there is a problem that the error correction apparatus cannot follow local offset fluctuations and amplitude fluctuations.

  The present invention has been made in view of the above background, and an object of the present invention is to provide an advantageous technique for calculating the position or angle of a detection target with high accuracy and high speed, for example.

  One aspect of the present invention relates to a signal processing device, and the signal processing device includes a first positive phase signal (A) provided from a detection device for detecting a position or an angle of a detection target, the first A first antiphase signal (A ′) having a phase opposite to the positive phase signal (A), a second positive phase signal (B) having a phase different from that of the first positive phase signal (A), and the first It is configured to calculate the position or angle of the detection object based on the second antiphase signal (B ′) having an antiphase with respect to the two positive phase signals (B), and (A−A ′) as a cosine signal / (A + A ′), a first calculation unit for calculating (B−B ′) / (B + B ′) as a sine signal, and the position or angle of the detection object based on the cosine signal and the sine signal A second computing unit for computing.

  According to the present invention, for example, an advantageous technique for calculating the position or angle of a detection target with high accuracy and high speed is provided.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a diagram showing a schematic configuration of a signal processing apparatus according to a preferred embodiment of the present invention. The signal processing apparatus SP according to a preferred embodiment of the present invention is a periodic signal A, A ′, B, B ′ provided from a detection apparatus (for example, an encoder or a laser interferometer) that detects the position or angle of a detection target. Receive. The periodic signals A, A ′, B, and B ′ are signals whose phases change according to the position or angle of the detection target. Here, the periodic signals A and B are sinusoidal signals having a phase difference (ideally a phase difference of 90 °). The periodic signals A ′ and B ′ are signals having opposite phases to the periodic signals A and B (signals having a phase difference of 180 ° with respect to the periodic signals A and B), respectively. The periodic signal A can be considered as a first positive phase signal, the periodic signal A 'as a first antiphase signal, the periodic signal B as a second positive phase signal, and the periodic signal B' as a second antiphase signal.

  These periodic signals are signals that are detected by different light receivers in the detection device, and depending on the change in the position or angle of the detection target by each light receiver by the design of an appropriate optical system, FIG. The periodic signals A, A ′, B, and B ′ as illustrated in FIG. Here, the lower end of FIG. 2 is the zero level of the signal (that is, the signal level when no light is incident), and the upper end of FIG. 2 is the maximum level of the signal (that is, the maximum design level in the electronic circuit). is there.

  When amplitude-modulating noise e is superimposed on the periodic signals A, A ′, B, and B ′, the periodic signals A, A ′, B, and B ′ are added to the signal values shown in FIG. ) Is multiplied by the value. Here, e is a positive and negative minute value indicating noise, and may be a random value including various frequency components. Amplitude-modulating noise can be caused by, for example, fluctuations in light source intensity and power supply voltage in the detection device, so that the same value coefficients can be superimposed on all periodic signals A, A ', B, B'.

  Here, as an example, a case is considered in which the sensitivity of the light receiver corresponding to the periodic signal B or the amplification factor of the amplifier that amplifies the output of the light receiver is low. In this case, for example, the periodic signal B can be reduced proportionally as exemplified by B ″ (dotted line) in FIG. 2. If such a signal B ″ is processed as it is, the amplitude-modulating noise is effective. Therefore, it is preferable to adjust the amplification factor at the first stage of the signal processing device SP so as to have the same level as the amplitude of other periodic signals.

  In the signal processing device SP shown in FIG. 1, the amplitude correctors 1-1 to 1-4 constituting the amplitude correction unit compensate for the sensitivity difference between the light receivers of the detection device and the difference in amplification factor between the amplifiers. The amplitude correctors 1-1 to 1-4 output periodic signals with the amplitudes corrected so that the amplitudes of the periodic signals A, A ', B, and B' coincide with each other. For example, when the combination of the detection device and the signal processing device SP is determined, the amplification factors of the amplitude correctors 1-1 to 1-4 are adjusted by means such as a trimmer (semi-fixed variable resistor) or laser trimming. can do. Further, when it is uncertain what kind of detection device is connected to the signal processing device SP, for example, the amplification factors of the amplitude correctors 1-1 to 1-4 are individually adjusted using a digital trimmer. Is preferred. Or you may add the multiplier which correct | amends an amplitude by multiplying the digital data after AD conversion by AD converter 2-1 to 2-4 by a constant.

  For simplification of description, hereinafter, the periodic signals after the amplitude is corrected by the amplitude correctors 1-1 to 1-4 will be further converted by the AD converters 2-1 to 2-4. The periodic signals after being converted into digital data are also expressed as periodic signals A, A ′, B, and B ′.

  The amplitude correctors 1-1 to 1-4 output from the amplitude correctors 1-1 to 1-4 are converted into digital signals by the AD converters 2-1 to 2-4, and the subsequent processing is converted into digital data. It is converted and processed by the digital signal processor DSP. The digital signal processor DSP can be configured, for example, by a dedicated circuit, by incorporating software in a microprocessor, or by programming a field programmable gate array (FPGA).

  In the digital signal processing unit DSP, the first calculation unit 10 including the first calculation unit 10 and the second calculation unit 20 calculates (A−A ′) / (A + A ′) as a cosine signal and ( BB ′) / (B + B ′) is calculated. The second calculation unit 20 calculates the position or angle of the detection target based on the cosine signal and the sine signal.

  The first arithmetic unit 10 includes subtracters 3-1 and 3-2, adders 4-1 and 4-2, and dividers 5-1 and 5-2. The subtractor 3-1 receives the periodic signals A and A ′ converted into digital data, and calculates (A−A ′), which is the difference between the periodic signals A and A ′. The adder 4-1 receives the periodic signals A and A ′ converted into digital data and calculates (A + A ′) which is the sum of the periodic signals A and A ′. The divider 5-1 receives (A−A ′) and (A + A ′) as inputs, and calculates (A−A ′) / (A + A ′) = a, which is the ratio between them. The subtractor 3-2 receives the periodic signals B and B ′ converted into digital data and calculates (B−B ′), which is the difference between the periodic signals B and B ′. The adder 4-2 receives the periodic signals B and B 'converted into digital data, and calculates (B + B') which is the sum of the periodic signals B and B '. The divider 5-2 takes (B−B ′) and (B + B ′) as inputs and calculates a ratio (B−B ′) / (B + B ′) = b.

  Here, when amplitude-modulating noise e is superimposed on periodic signals A, A ′, B, and B ′, that is, (1 + e) is applied to periodic signals A, A ′, B, and B ′. Consider the case of multiplication. As apparent from the following equation, the noise e is removed from the signals a and b output from the dividers 5-1 and 5-2.

{(1 + e) A− (1 + e) A ′} / {(1 + e) A + (1 + e) A ′} = (A−A ′) / (A + A ′) = a
{(1 + e) B− (1 + e) B ′} / {(1 + e) B + (1 + e) B ′} = (B−B ′) / (B + B ′) = b
Here, a is a sinusoidal periodic signal and can be considered as a cosine signal, and b is a sinusoidal periodic signal having a phase difference of 90 ° from a and can be considered as a sine signal.

  The second calculation unit 20 performs correction calculation and arc tangent calculation according to a known method with the cosine signal a and the sine signal b output from the dividers 5-1 and 5-2 as inputs. FIG. 1 shows a configuration example of the second calculation unit 20. The first error corrector 6-1 corrects the error of the cosine signal a using the error estimated value and generates a corrected cosine signal. The second error corrector 6-2 corrects the error of the sine signal b using the estimated error value and generates a corrected sine signal. In many cases, an offset error that is a positive / negative imbalance in each of the cosine signal a and the sine signal b and an amplitude error that is a difference in amplitude between the cosine signal a and the sine signal b are removed at this stage.

Hereinafter, the operation of the second calculation unit 20 will be described in more detail. First, second error corrector 6-1 and 6-2, the cosine signal a, as an input sine signal b, the offset error Z A to be estimated, Z B and the amplitude G A, based on the G B, the following According to the equation, the cosine signal A * and the sine signal B * with corrected errors are generated.

A * = (a-Z A ) / G A
B * = (b-Z B ) / G B
The phase calculator 7 performs arctangent calculation (that is, atan −1 (A * / B * )) using the cosine signal A * and the sine signal B * whose error has been corrected, and detects the position of the detection object or Outputs information indicating the angle.

The peak value collectors 8-1 and 8-2 respectively collect the maximum value and the minimum value of the cosine signal A * and the sine signal B * . The cosine signal A * has a maximum value at 0 ° and a minimum value at 180 °. Therefore, the amplitude G A * of the cosine signal A * can be estimated by subtracting the value of 180 ° from the value of 0 ° of the cosine signal A * (that is, by obtaining 2G A * ). The average of the maximum value and the minimum value is an offset error Z A. Since the sine signal has a maximum value at 90 ° and a minimum value at 270 °, the error (amplitude G B * , offset error Z A * ) of the sine signal can be estimated by the same procedure.

The cosine signal A * is a normalized signal, and ideally G A * should be 1 and Z A * should be 0, but the error correction units 6-1 and 6-2 used for normalization calculation. offset errors Z a, Z B and the amplitude G a, when there is an error in the estimated value of G B is biased may occur from these ideal values. Therefore, by correcting the estimated values of the offset errors Z A and Z B and the amplitudes G A and G B used for normalization using all or part of these deviations, these estimated values are always set to correct values. Can keep.

  As described above, the amplitude-modulating noise does not affect the phase calculation using the signal ratio but affects the peak value. For this reason, when the amplitude modulation noise is not removed, the error correction unit is affected by the noise, and the error correction cannot be performed with high accuracy. If a large number of peak values are averaged, the influence of noise can be suppressed. However, in this case, there arises a problem that the responsiveness to fluctuations in the amount of mixed errors deteriorates.

  According to a preferred embodiment of the present invention, it is possible to improve both accuracy and responsiveness by removing amplitude-modulating noise before arctangent calculation. For this reason, it is possible to meet a wide range of demands for accuracy improvement in the field and angle measurement fields that require particularly high accuracy. The configuration for removing amplitude-modulating noise can be realized by a simple arithmetic unit such as a subtracter, an adder, and a divider.

  Here, correction of offset error and amplitude error has been described as an example of error correction technology. However, various other error removal techniques are known today, and amplitude-modulated noise removal is expected to have an effect of improving accuracy and responsiveness even in these various error correction techniques. The

It is a figure which shows schematic structure of the signal processing apparatus of suitable embodiment of this invention. It is a figure which illustrates a two-phase periodic signal.

Claims (4)

  1. A first positive phase signal (A) provided from a detection device for detecting the position or angle of the detection object, and a first negative phase signal (A ′) having an opposite phase to the first positive phase signal (A) ), A second positive phase signal (B) having a phase different from that of the first positive phase signal (A), and a second negative phase signal (B) having a phase opposite to that of the second positive phase signal (B). ') Is a signal processing device that calculates the position or angle of the detection object based on
    A first calculation unit that calculates (A−A ′) / (A + A ′) as a cosine signal and calculates (B−B ′) / (B + B ′) as a sine signal;
    A second computing unit that computes the position or angle of the detection object based on the cosine signal and the sine signal;
    A signal processing apparatus comprising:
  2.   The amplitudes of the first positive phase signal (A), the first negative phase signal (A ′), the second positive phase signal (B), and the second negative phase signal (B ′) are made to coincide with each other. The signal processing apparatus according to claim 1, further comprising an amplitude correction unit.
  3. The second calculation unit includes:
    A first error corrector that corrects an error of the cosine signal to generate a corrected cosine signal;
    A second error corrector that corrects an error of the sine signal to generate a corrected sine signal;
    A phase calculator that performs arctangent calculation based on the corrected cosine signal and the corrected sine signal,
    The signal processing apparatus according to claim 1, wherein:
  4. The first error corrector and the second error corrector correct an offset error and an amplitude error;
    The signal processing apparatus according to claim 3.
JP2009009365A 2009-01-19 2009-01-19 Processing apparatus Withdrawn JP2010164541A (en)

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JP5079346B2 (en) * 2007-01-30 2012-11-21 東芝機械株式会社 Waveform correction apparatus and waveform correction method
WO2013134255A1 (en) 2012-03-05 2013-09-12 Gsi Group Corporation Phase estimation method and apparatus therefor
WO2014198344A1 (en) * 2013-06-14 2014-12-18 Aktiebolaget Skf A method for dynamic normalization of analogue sine and cosine signals, a sensor or a sensor bearing unit and a mechanical device

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US4458322A (en) * 1981-06-19 1984-07-03 Manhattan Engineering Co., Inc. Control of page storage among three media using a single channel processor program and a page transfer bus
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